Heat regenerators can be found in a considerable number of engineering applications, and are either used as pair of fixed matrices or as single rotary matrix. These matrices are composed of numerous channels, traditionally of about a few millimeters in diameter. The thermal design of heat regenerators is usually done considering models that rely on well-established simplifying assumptions. Most of these assumptions are valid for mini- and larger scale channels; nevertheless, with the growing tendency towards miniaturization, mini- to micro-scale channels come into play. As a result some classical simplifying assumptions may no longer be applied to reduced-size channels. One such effect is that of rarefaction, in which the mean free path of the molecules can no longer be considered negligible. In this context, this paper proposes an investigation on how rarefaction and additional effects encountered in regenerative heat exchange (such as a transient regime and thermal wall storage) can influence the heat transfer coefficient. The obtained results can be of assistance in achieving better thermal designs for miniaturized heat exchangers.

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